To edit your profile, including adding your profile's image, click the drop down menu in the upper right corner of your account and click on your name.
To edit your profile bio, simply type in the changes and press save.
To upload (or edit) your profile picture, click Photo on the left hand side. Then choose an image from your computer to upload. Once it's uploaded, crop it (if necessary) and then press save.
If you have any difficulty updating your profile, please don't hesitate to contact Udemy Support.